A telephone conference call is a means by which multiple participants communicate by calling into a conference “bridge,” a system that enables all of the call's participants to hear each other. The bridge is typically part of a conferencing server, a data-processing system that fulfills conferencing service requests from its users. The conferencing server enables dial-in and dial-out conferencing that involves two or more telecommunications terminals. Such terminals include plain old telephone service (POTS) telephones, packet-capable telephones, personal computers that comprise softphone or other communications functionality, and so forth.
The bridging function in a conferencing server mixes media signals, for each participant, from other sources on a conference call. Although typically the media signals that are mixed are voice signals, other media signals such as non-voice audio and video signals can also be mixed. The conferencing server provides the mixed signals to each participant so that the participants on the conference call can hear or otherwise communicate with each other.
The problem with mixing the signals is that if there is an impairment that is received on one of the signal paths, such as noise from one of the telephones involved, then that impairment usually ends up being mixed into the composite signal made available to all of the participants. Therefore, even if one signal path is the source of an impairment, all of the participants might hear the impairment, thus diminishing the conferencing experience.
Various techniques in the prior art deal with how a signal impairment such as noise is suppressed or at least mitigated. Some of those techniques are applied to the telecommunications terminal, while other techniques are applied to the intermediate signal path, while still other techniques are applied to the conferencing server end. Those prior art techniques are intended to improve the conferencing experience in that they attempt remove or reduce the problem—that is, the presence of signal impairments.